Kennedy Jr.'s secrets to longevity and a fit appearance lie in three core methods: intermittent fasting, weekly weight training, and daily mountain climbing to build a lean, muscular body.

In a 2023 interview with Lex Fridman, a computer scientist and popular podcast host, Kennedy Jr. stated he practices "intermittent fasting", which means fasting for 18 hours and eating only within the remaining 6-hour "window". This method is also known as the 18/6 fasting regimen. He typically has his first meal around noon and tries not to eat after 6-7 p.m.

Proponents of the 18/6 method believe that limiting eating times helps with weight loss, reduces inflammation, and improves heart and brain health. This method offers numerous health benefits, such as reducing oxidative stress and chronic inflammation, lowering levels of bad cholesterol (LDL) and triglycerides, and promoting autophagy to eliminate damaged cells. Additionally, fasting helps increase growth hormone secretion, improves blood sugar regulation, and reduces the risk of cancer, heart failure, or neurological decline.

Secretary Robert F. Kennedy Jr. in a birthday photo posted on the HHS X account on 17/1. Photo: HHS

Secretary Robert F. Kennedy Jr. in a birthday photo posted on the HHS X account on 17/1. Photo: HHS

Alongside his diet, he maintains a high level of physical activity despite being in his 70s. His daily routine includes mountain walking. "The first thing I do in the morning is attend a 12-step meeting, then I walk and climb hills," Kennedy Jr. explained to host Fridman when asked about his exercise habits. "I walk about 2.4 km uphill and 2.4 km downhill with my dogs, then I spend time meditating."

Kennedy Jr. shirtless, cycling, and taking an ice bath challenge while still wearing jeans in a workout video with musician Kid Rock on 16/2. Video: X

Walking 2.4 km uphill and 2.4 km downhill each way means he walks a total of 4.8 km every day. According to the Ramblers organization, the average walking speed for an adult is about 4 km/h, meaning it takes about 15 minutes to complete 1 km.

Thus, he would spend about 72 minutes on his daily journey of over 4.8 km. If he maintains this routine every day of the week, he achieves 504 minutes of moderate-intensity cardio each week, equivalent to nearly 8.5 hours.

With a total walking time of about 72 minutes daily, Kennedy Jr. far exceeds the World Health Organization (WHO) recommendation of 150 minutes per week. Mountain climbing not only boosts cardiovascular health and metabolism but also builds muscle endurance; the uphill climb increases heart rate and burns calories effectively, while the downhill segment strengthens the quadriceps and core muscles.

In addition to mountain walking for cardiovascular training, his workout schedule also focuses on strength training exercises. He stated he has maintained gym workouts for the past 50 years, with 4 weight training sessions per week, each lasting 35 minutes. His training schedule is specifically divided by muscle group: one day for back, one day for chest, one day for legs, and one day for full body.

In each workout, Kennedy Jr. typically performs the first set with 12 repetitions until the muscle is completely fatigued, and the final set uses the "drop set" method, continuously reducing the weight to push muscles to their limit. His training style involves high resistance and almost no rest between exercises, similar to circuit training.

This method plays a key role in building muscle, maintaining basal metabolic rate, and combating age-related muscle loss.

Beyond physical training, Kennedy Jr. also revealed that he supplements with a variety of essential vitamins and nutrients daily. "I take a lot of vitamins, so many I can't even list them all here because I can't remember them, but in short, I ingest a large amount of vitamins and nutrients," he said in the podcast interview.

Kennedy Jr. working out shirtless at Gold’s Gym in California, US, in 2023. Video: Instagram

He also admitted to following an anti-aging protocol from a doctor, which includes testosterone replacement therapy (TRT), but emphasized that he does not use muscle-enhancing steroids or any similar substances.

The TRT Kennedy Jr. uses is bio-identical, fully compatible with what the body naturally produces. Typically, after age 30, testosterone levels in men decrease by 1-2% each year, leading to conditions such as reduced libido, muscle loss, fatigue, and depression.

Hormone supplementation, when prescribed by a specialist, can improve these symptoms, but potential risks related to the prostate and excessive red blood cell increase must be carefully considered.

Robert F. Kennedy Jr.'s "muscular physique" at 72 is the result of half a century of sustained persistence. The close combination of mountain climbing, weight training, intermittent fasting, and expert-guided body index management stands as a testament to the power of discipline and a scientific lifestyle in conquering time.

Kennedy Jr. in a workout video on 16/2. Screenshot: X

Kennedy Jr. in a workout video on 16/2. Screenshot: X

Binh Minh (According to Marathon Handbook, Lex Fridman Podcast)